so i have a 1998 integra gsr with a goal of about 200whp in mind. my current set up is diy ice box and apexi ws2 catback. i already order the rmf header and a vibrant high flow cat but after some researching on exhaust i pick up that u should match the pipe size or go from smaller to bigger and not bigger to smaller. which in my case it will be 2.5(rmf header) 2.25(high flow cat) 2.36 (ws2). so my question is how bad of a restriction will my current setup be on a n/a 200whp goal be? i already have restriction with a chamber ws2 and a high flow cat so i don't want to make it any worse with a bottleneck exhaust. i was thinking of selling the rmf locally and try to find a 2.25 header but only came across dc sport(which has a lot of bad review) and usdm itr header.

 

The whole exhaust after the header is a restriction. The actual merge is also smaller than 2.5" on a real rmf. 2.5" was just the exit size. Anyway, it depends on what you want. Go bigger and you make more power yet sacrifice sound/loudness.

Also, no point in making a whp goal without knowing what you make now.

Read the faq.

 

after reading the faq i also get ur point but im just trying to squeeze as much power as i can out of the engine with the bolt on and tune. after looking at many dyno and built thread i understand that i wont be getting the same number but im not expecting anything big out of this, ill be happy just to be within the 180 range . this is just a dd that im trying to squeeze whatever power i can get out of it. i also just want to know if this setup work together or it will backfire. so how bad is it if the piping diameter change after the 2.5 exit.(header 2.5 exit to a 2.25cat to 2.36 catback) or since it just the exit size of the header it wont effect?

 

I have a built b20v with a 2.5 header to 2.5 test pipe to a 2.36 apexi noir catback, never backfire. I went with the apexi noir catback due to sound because where i live cops give you fixing tickets.

 

oh sorry i didn't mean backfire as the car will backfire. what i meant was by doing different diameter piping will that effect the performance by a lot or it doesn't effect it to a point where it isn't a big difference since it n/a. i read this exhaust article where bottleneck exhaust cause more restriction to the flow. where u either go same diameter all around or smaller(header) to bigger (muffler). i know for a turbo car it will effect it but for a n/a would it be that big of a deal?

 

Your info is backwards. you want a larger collector or a collector that matches the exhaust. 2.25 "" collector is too small for that whp goal. your rmf will be fine and so will your exhaust. I would get a 2.5" cat to match your end collector. investing in a good set of cams and a tune will be your best bet. do not get a skunk 2 manifold. the performer x manifold is better for your goals. I am running a mild set of cams and some simple off the shelf bolt ons and I'm close to hitting 200who..

 

he doesnt have a big enough engine to warrant a "big" collector"

 

Have a look at this https://www.privatelabelmfg.com/prod...b20-header.htm I have it and I like it made a thred about it some time ago most ppl who gave input also agreed. (hytech rep) but if you don't live in Cali consider a test pipe they're all 2.5(just over/just under) as far as the exhaust if you want a TRUE ID of 2.5 here: http://store.skunk2.com/exhaust-tuni...-exhausts.html

all depends on you'r plans in the end as DazeMs said good cams+tune will be you'r main power source at the end.

 

i installed one on an integra although I didnt want to for various reasons. It was awful to assemble and even at stock height, the bottom of the header scraped. I expected it to fit like crap but not that bad.

 

Assembly was a 2 person job with mine haha but we did it before we put it on the car which proved to be a big PITA to get under it tho(2'' drop all around). mine has scraped many a time but i do like it it's pretty tough has a minor dent but nothing "compramising".

 

If u want good ground clearance, go with the plm smsp rep header. Only downfall on these is that u will have to get a pusher fan because the header sticks too far out unless ur running stock radiator

 

i also agree with 98vtec that 2.5 a bit big. now i know a lot of people on h-t making 200+ whp with a 2.5 exhaust but that them trying to go beyond(which i'm not trying to doing lol)or fastest way possible. Would me making a 2.25 slip on joint for my rmf solve my problem and get rid of the bottleneck? or is the 2.5collector/2.5hi flow cat/2.36 ws cat back set up isn't that big of a problem where the difference is night and day. i just want everything to work well together and not just throw random part together where it will have a negative effect. i know the way I'm doing stuff it will be harder to have the best of both world(nearly stock exhaust sound + 180-200wph) with a chamber exhaust system but i believe with the right part and a good tuner(evan tuner in PA) i think ill get close to it. thank you so much guys for the input

 

the actual choke on the rmf (the end of the merge collector where they all come to one) is not 2.5". Not sure on the replica's. probably didnt factor that into their copy.

 

I think it should be fine, like I said I'm running 2.5 header to 2.5 test pipe to 2.36 cat back exhaust system.

 

A 2.5" collector is not too large. Jdm type r's runs factory 4-1 with 2.5" collector for sakes. I'm currently running a 2.5 collector+2.5" highflow cat + 2.25id. exhaust. 185whp /138ftlbs. With mild cams on 87 octane b18c1

 

Tuned right ? just wondering about that 87 wouldn't mind paying less for gas if it works lol, no knocking ? in theory wouldn't you make more with 93/94 tho

 

Yup.. tuned on 87.

 

Ok? There is more to header design than the collector. My race car runs a 2.5" choke and every race header company i spoke with recommended 2.375" with a 4" megaphone exit and a reverse cone. And my race motor is almost 2.4L and makes power above 9000.

 

Your really going to try an argue about a 2.5" od collector, when you've got threads in this forum telling people to run 3"id exhaust piping? The 2.25"od collectors are too small for anything above factory style performance. but feel how you wish.

 

says who? wheres your data to back this up? are you familiar with the different parts of an exhaust system? i think you are possibly getting confused.

exhaust manifold design is COMPLETELY separate from any exhaust sizing/design after the extension of the collector choke. That extended portion of piping after the choke is very important as well.

yes. I will argue that. Exhaust piping sizing vs. header sizing/length along with collector sizing/length/angle/design/megaphone design....yes, different.


ask yourself what the REAL points are of the exhaust after the exhaust manifold is finished doing its job.

 

Wow... your reading way more into it then what I was getting at.. don't question things that aren't even there . I'm not even going to argue with you as I see no worth in this. have a nice day.

 

Because you're talking about exhaust velocity. The whole "backpressure" thing is a myth and has been proven since.. I follow what you're saying however, MOST custom header builders will use different choke points and then megaphone out, this helps create faster speed and high velocity of the exh gases when it exits.

this is actually a good read, i found a few nights ago http://www.x-pipe.com/Scavenge.html

Not arguing neither, dont take it as such.

 

Sure thing.

btw, arguing and discussing are, as well, two different things.

 

thank you guys for the great info ( especially DDTECH) that really is a good read. im probably going to just slap on the stuff for now since i already order them and work on the intake/cams side. probably will redo the exhaust system after a dyno run(if the number isnt so great) and get some advice from the tuner and see what can be done/fix. once again tyvm everyone for the info

 

OP I sent you a pm reguarding cams.